Public Lecture /公开讲座 (45 min)
Speaker: Di Li, Professor, Dr.
演讲人：李菂 教授
Affiliation: Tsinghua University, National Astronomical Observatories, Chinese Academy of Sciences, China
单位：清华大学，中国科学院国家天文台
Title: “Time Frontier: Extending Human Cognizance of the Dynamic Universe”
Abstract:
Modern physics and astronomy both originated from Galileo. Since Galileo’s pioneering use of telescopes, optical observations have been dominating astronomy. Hertz invented the first antenna and demonstrated the wave-particle duality of light. These developments give rise to radio astronomy and giant dishes.
The 20th century saw the advent of a scientific and technical wonder that is Arecibo. Since its inception in November of 1963 as a direct result of the cold war, the Arecibo telescope perched on the apex of human antenna for more than half a century, generating a series of landmark discoveries, including the double neutron star that won the Nobel prize in 1993.
First proposed in 1990s, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) started full operation in early 2020. Since then it has become a leading observatory in radio astronomy, facilitating 12 Nature/Science (main journal) publications in its first 5 years.
Most of the major discoveries so far from FAST came from its 19-beam system, which was built by the same group who has built the Parkes 13-beam system. Parkes became famous when it broadcasted the first Apollo landing. As a major upgrade to Parkes telescope, its multi-beam system transformed single-dish radio astronomy, delivering the largest haul of new pulsars, definitive HI galaxy catalogues, and the standard HI maps of the Southern sky. These landmark surveys had to be conducted separately, due to the conflicting observation requirements. We invented the high-cadence CAL technique, in which the calibration signal is injected at the sampling rate and facilitate, for the first time, truly commensal pulsar and spectral-line surveys. Implemented on FAST with drift-scan mode, the Commensal Radio Astronomy FAST Survey (CRAFTS) has multiplied the survey efficiency of FAST an discovered more than 260 pulsars as well as 10 Fast Radio Bursts (FRBs) and released over 5,000 square degrees of calibrated HI images. I will report a few science highlights from CRAFTS, in the context of surveying the dynamic radio sky.
The experience of setting up high-cadence surveys also lead to a few recent discoveries, including the first radio pulsar from a Central Compact Object (CCO) with the MeerKAT array and the first long-period-transient (LPT) residing in a supernova remnant with the DART array. These recent discoveries from radio telescopes world-wide are filling in the missing puzzles of a richer and more complete picture of compact objects, which started by Landau’s suggestion of a ‘giant nucleus’, elucidated by Baade & Zwicki’s invention of the terms of supernova as well as neutron stars, make prominent by Bell’s discovery of pulsars that won the Nobel prize in 1974.
CRAFTS' high cadence sampling of the radio sky also give rise to the concept of the "time frontier". I coined this term to represent the quantum foundation of the Universe that is to be revealed by exploring extreme transients. Hypothetical considerations will be given to possible lines of investigations.
Biography:
Dr. Di Li is a distinguished radio astronomer, currently serving as a Chair Professor at Tsinghua University and former Chief Scientist of the Five-hundred-meter Aperture Spherical Telescope (FAST), China’s national major scientific infrastructure. He has pioneered several innovative observational and data analysis techniques, including the HI Narrow Self-Absorption (HINSA) method and a novel inversion algorithm for solving dust temperature distributions—these technologies have provided critical support for measuring key physical parameters of star-forming regions, with related findings (e.g., studies on star formation time scales and interstellar magnetic fields) featured as a cover article in Nature.
Dr. Li has led or contributed to numerous landmark scientific discoveries, such as the first detection of interstellar molecular oxygen, the identification of the first persistently active Fast Radio Burst (FRB), and the largest FRB sample set to date. He is currently leading the Commensal Radio Astronomy FasT Survey (CRAFTS)—the world’s first commensal survey simultaneously covering HI (neutral hydrogen), pulsars, and FRBs. To date, CRAFTS has discovered over 200 pulsars, more than 8 FRBs, and released 5,000 deg2 HI sky maps.
With over 350 peer-reviewed journal articles published and more than 10,000 total citations, Dr. Li was awarded the 2024 Marcel Grossmann Award "for his groundbreaking contributions to the scientific definition of the world’s most sensitive radio telescope and his numerous innovations in characterizing the dynamic universe." His other prominent honors and leadership roles include: the 2005 National Research Council (US) Resident Research Fellowship (awarded through national competition "in recognition of his outstanding research capabilities"); the 2022 Distinguished Achievement Award of the Chinese Academy of Sciences (CAS); the 3rd National Innovation Award; membership on the Steering Committee of the Australia Telescope National Facility (ATNF); the Science and Engineering Advisory Committee (SEAC) of the Square Kilometer Array (SKA); and the advisory panel of the Breakthrough Listen initiative.
More details can be found at the webpages:
https://baike.baidu.com/item/%E6%9D%8E%E8%8F%82/9119504
李菂 教授简介：
李菂博士是享誉国际的射电天文学家，现任清华大学讲席教授，曾任国家重大科技基础设施 ——500 米口径球面射电望远镜（FAST，简称 “中国天眼”）首席科学家。他开创了多项创新性观测与数据分析技术，包括中性氢窄自吸收（HINSA）方法及求解尘埃温度分布的新型反演算法 —— 这些技术为恒星形成区关键物理参数的测量提供了核心支撑，相关研究成果（如恒星形成时标、星际磁场研究）已作为封面文章发表于《自然》期刊。
李菂博士主导或参与了多项具有里程碑意义的科学发现，包括首次探测到星际分子氧、确认首个持续活跃的快速射电暴（FRB） ，以及构建了迄今规模最大的快速射电暴样本集。他目前牵头开展 “共焦射电天文快速巡天”（CRAFTS）项目 —— 这是全球首个同时覆盖中性氢（HI）、脉冲星与快速射电暴的共焦巡天计划。截至目前，CRAFTS 项目已发现 200 余颗脉冲星、8 颗以上快速射电暴，并发布了覆盖 5000 平方度的中性氢天图。
李菂博士已发表同行评审期刊论文 350 余篇，总被引次数超 10000 次。他因 “在全球最灵敏射电望远镜的科学定义方面作出开创性贡献，且在动态宇宙表征领域提出多项创新成果”，荣获 2024 年度马塞尔・格罗斯曼奖（Marcel Grossmann Award）。其其他重要荣誉与学术职务包括：2005 年经全美竞争入选美国国家研究委员会（National Research Council, US）驻校研究员（表彰 “其杰出的科研能力”）；2022 年度中国科学院杰出成就奖；第三届全国创新争先奖；澳大利亚望远镜国家设施（ATNF）指导委员会委员；平方公里阵列（SKA）科学与工程咨询委员会（SEAC）委员；“突破聆听”（Breakthrough Listen）计划顾问组成员等。